1. Field of the Invention
The present invention relates to an asymmetric scroll compressor, and more particularly, the present invention relates to an asymmetric scroll compressor which can minimize a reverse rotation torque of an orbiting scroll, keep constant a direction of force acting on an Oldham ring to prevent reversal of rotation toque of the orbiting scroll, and reduce to the minimum unbalanced force of discharging gas generated upon a discharging stroke.
2. Description of the Related Art
Generally, a compressor serves as a machine for compressing fluid such as air, refrigerant gas or the like. The compressor is composed of a power generating section for generating driving force and a compressing mechanism section for compressing gas using the driving force which is transferred from the power generating section. Compressors are generally divided into rotary compressors, reciprocating compressors and scroll compressors, depending upon structures of compressing mechanism sections.
FIG. 1 illustrates a compressing mechanism section of a scroll compressor. As shown in FIG. 1, a compressing mechanism section of a scroll compressor includes a frame 1. n orbiting scroll 4 which has a wrap 4a of an involute curve-shaped configuration, is seated on an upper surface of the framer. A fixed scroll 3 is coupled to the orbiting scroll 4 in such a way as to cover the orbiting scroll 4. The fixed scroll 3 is formed, on a lower surface thereof, with a wrap 3a which has an involute curve-shaped configuration, and is defined, at a center portion thereof, with a discharging hole 3b. The fixed scroll 3 and the orbiting scroll 4 cooperate with each other to define compression chambers P therebetween. A boss part 4b which is projectedly formed on a lower surface of the orbiting scroll 4, is connected with an eccentric part 2a of a rotation shaft 2 which in turn is connected with a power generating section (not shown).
An Oldham ring 30 for preventing rotation of the orbiting scroll 4 is disposed between the frame 1 and the orbiting scroll 4.
FIG. 2 illustrates in further detail a coupling relationship of the Oldham ring 30 As shown in FIG. 2, the Oldham ring 30 has a ring-shaped configuration. First and second keys 32 and 33 each having a square column-shaped configuration are projectedly formed on an upper surface of the Oldham ring 30 and located along a first straight line. Third and fourth keys 34 and 35 each having a square column shaped configuration are projectedly formed on a lower surface of the Oldham ring 30 and located along a second straight line which is orthogonal to the first straight line along which the first and second keys 32 and 33 are located.
The lower surface of the orbiting scroll 4 is defined, along the first straight line, with first and second key grooves 4c and 4d, in a manner such that the first and second keys 32 and 33 of the Oldham ring 30 are respectively fitted into the first and second key grooves 4c and 4d. Also, the upper surface of the frame 1 is defined, along the second straight line, with third and fourth key grooves 1a and 1b, in a manner such that the third and fourth keys 34 and 35 of the Oldham ring 30 are respectively fitted into the third and fourth key grooves 1a and 1b. 
The Oldham ring 30 is disposed between the frame 1 and the orbiting scroll 4, so that the first and second keys 32 and 33 are respectively fitted into the first and second key grooves 4c and 4d of the orbiting scroll 4 and the third and fourth keys 34 and 35 are respectively fitted into the third and fourth key grooves 1a and 1b of the frame 1.
In the compressing mechanism section, if driving force is transferred from the power generating section to the rotation shaft 2, the orbiting scroll 4 which is secured to the rotation shaft 2, is orbited in a state wherein the orbiting scroll 4 is engaged with the fixed scroll 3 and prevented by the Oldham ring 30 from being rotated. By orbiting motion of the orbiting scroll 4, relative movement of the wraps 3a and 4a which are respectively formed on the fixed scroll 3 and the orbiting scroll 4 and each of which has the involute curve-shaped configuration, is induced, whereby it is possible to continuously intake, compress and discharge gas.
Hereinbelow, a compression principle of the scroll compressor will be described with reference to FIG. 3. By the fact that the fixed scroll 3 which has the wrap 3a of the involute curve-shaped configuration and the orbiting scroll 4 which has the wrap 4a of the involute curve-shaped configuration, are engaged with each other in a state wherein the wraps 3a and 4a have a phase difference of 180xc2x0 therebetween, crescent-shaped compression chambers P are respectively created at opposite positions. In this situation, when the orbiting scroll 4 is orbited with respect to the fixed scroll 3 which is secured to the frame 1 in a state wherein the orbiting scroll 4 is prevented by the Oldham ring 30 from being rotated, as the compression chambers P are moved toward a center of the scroll compressor, volumes of the respective compression chambers P are reduced and thereby a compressing function of the scroll compressor is performed.
More concretely speaking this compressing procedure, refrigerant gas which is introduced into the scroll compressor, flows into the fixed scroll 3 through an intake port (not shown) which is defined through a side wall of the fixed scroll 3.
At this time, one part of the intaken gas flows into a first compression chamber P1 which is defined adjoining the intake port of the fixed scroll 3, and then, a compressing process is undertaken. At the same time, the other part of the intaken gas flows, along a guide passage which is defined through the fixed scroll 3, into a second compression chamber P2 which is defined directly opposite to the first compression chamber P1 to be placed at a 180xc2x0 separation from the first compression chamber P1, and then, a compressing process is undertaken. As the orbiting scroll 4 is orbited, the refrigerant gas existing in the compression chambers P, which refrigerant gas is undertaken to be symmetrically and simultaneously compressed, is further compressed while being moved toward the center of the scroll compressor, and then, is discharged through the discharging hole 3b which is defined at the center portion of the fixed scroll 3.
On the other hand, in the case of an asymmetric scroll compressor, as can be readily seen from FIG. 4, by the fact that a wrap 5a of a fixed scroll 5 is formed in such a way as to be longer than a wrap 6a of an orbiting scroll 6 by 180xc2x0 or less, it is possible to intake an increased amount of refrigerant gas into the same volume when compared to a conventional symmetric scroll compressor, whereby a stroke volume is raised. Also, because it is possible to prevent the refrigerant gas which is intaken into the compression chambers P, from being heated, an intake amount of the refrigerant gas can be further increased.
In the meanwhile, referring to FIG. 5, in the scroll compressor, a rotation torque of the orbiting scroll is calculated by an equation given below:
Mt=Ftxc3x97{xcex2xe2x88x92r cos (xcex4exe2x88x92xcex8)}
where Ft is gas force acting in a tangential direction, xcex2 is a distance from a center of the orbiting scroll to an application point of the gas force Ft, r is an eccentricity between a center of an end plate of the orbiting scroll and a center of a base circle of an involute curve of the orbiting scroll wrap, xcex8 is a crank angle, and xcex4be is an eccentric angle which is measured at an outer end of the wrap toward a direction where the wrap is wound up.
In the case of a conventional symmetric scroll compressor, due to the fact that pressures in two compression chambers are the same with each other, since xcex2 is constant as xc2xdxcex5 (that is, a half of an orbiting radius) and r=0, the rotation torque acts in a constant direction and thereby, behavior of the orbiting scroll is stabilized.
On the contrary, in the case of a conventional asymmetric scroll compressor, while the gas force Ft is unchanged, a value of xcex2 moves in a positive or negative direction due to asymmetry in pressures of the compression chambers which asymmetry is caused by a difference in an amount of intaken gas. Thus, the rotation torque Mt also moves in the positive or negative direction while the orbiting scroll is orbited. As a consequence, the orbiting scroll vibrates in forward and reverse orbiting directions.
FIG. 6 is a diagram illustrating a relationship between force which acts on the orbiting scroll and the keys of the Oldham ring in the just above-described condition, FIG. 7 is a graph illustrating a rotation torque which is applied to the orbiting scroll while the orbiting scroll is orbited in the just above-described condition, and FIG. 8 is a graph illustrating force which is applied to the keys of the Oldham ring due to the rotation torque of the orbiting scroll.
As shown in FIGS. 6 through 8, by the fact that the rotation torque and the reverse rotation torque act on the orbiting scroll in the positive and negative directions, because one or both of the keys 32 and 33 of the Oldham ring apply contact force toward both sides thereof, behavior of the orbiting scroll 6 and the Oldham ring 30 is made unstable. Further, due to the fact that the keys 32 and 33 of the Oldham ring 30 are brought into contact with the orbiting scroll 6 in a state wherein they are respectively fitted into key grooves 6b and 6c which are defined in the orbiting scroll 6, vibration noise and contact wear are generated. Moreover, by vibration of the orbiting scroll 6 in the forward and reverse orbiting directions, gaps are created in the compression chambers and thereby pressure leakage is caused.
In addition, in the case of the symmetric scroll compressor, since both compression chambers have the same pressure, volumetric ratios (that is, compression ratios) of both compression chambers are the same with each other upon a discharging stroke. However, in the case of the asymmetric scroll compressor, since both compression chambers have different pressures, pressure leakage increasingly occurs from one compression chamber having a high pressure to the other compression chamber having a low pressure.
Consequently, even in the case that volumetric ratios of both compression chambers are designed to be the same with each other, at the point of time when the discharging process is actually undertaken, pressures of both compression chambers are differentiated from each other. By this, due to the fact that one compression chamber is excessively compressed and the other compression chamber is insufficiently compressed, fluid loss is provoked upon the discharging stroke, and according to this, unbalance in gas force is deepened. Thus, a problem is caused in that behavior of the orbiting scroll is made unstable.
Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and an object of the present invention is to provide an asymmetric scroll compressor which can minimize a reverse rotation torque acting on an orbiting scroll in such a way as to stabilize behavior of the orbiting scroll, keep constant a direction of force acting on an Oldham ring in such a way as to stabilize behavior of the Oldham ring, and reduce to the minimum unbalanced force of discharging gas, generated upon a discharging stroke.
In order to achieve the above object, according to one aspect of the present invention, there is provided an asymmetric scroll compressor including an orbiting scroll having an end plate and a boss part which are concentrically formed and possessing a wrap which is formed on an upper surface of the end plate and has an involute curve-shaped configuration, an Oldham ring arranged on a lower surface of the orbiting scroll in such a way as to prevent the orbiting scroll from being rotated, and a fixed scroll covering an upper portion of the orbiting scroll and having a wrap which has an involute curve-shaped configuration and is engaged with the wrap of the orbiting scroll in a manner such that compression chambers are defined between the wraps of the orbiting and fixed scrolls by rotating motion of the orbiting scroll, the wrap of the fixed scroll further extending within the range of 180xc2x0 than the wrap of the orbiting scroll in a direction where an involute curve extends, wherein a center of a base circle of the orbiting scroll wrap is positioned within a region which ranges circumferentially between 30xc2x0 in a direction where the existing orbiting scroll wrap is extended and 60xc2x0 in a direction where the existing orbiting scroll wrap is wound up, when measured from a straight line connecting a center of a base circle of the existing orbiting scroll wrap which center corresponds to a center of the end plate and the boss part, with an outer end of the existing orbiting scroll wrap, and radially between 0.1 times and 0.5 times a orbiting radius of the orbiting scroll wrap.
According to another aspect of the present invention, there is provided an asymmetric scroll compressor including an orbiting scroll having an end plate and a boss part which are concentrically formed and possessing a wrap which is formed on an upper surface of the end plate and has an involute curve-shaped configuration, an Oldham ring arranged on a lower surface of the orbiting scroll in such a way as to prevent the orbiting scroll from being rotated, and a fixed scroll covering an upper portion of the orbiting scroll and having a wrap which has an involute curve-shaped configuration and is engaged with the wrap of the orbiting scroll in a manner such that compression chambers are defined between the wraps of the orbiting and fixed scrolls by orbiting motion of the orbiting scroll, the wrap of the fixed scroll further extending within the range of 180xc2x0 than the wrap of the orbiting scroll in a direction where an involute curve extends, wherein one of keys which are formed on upper surface of the Oldham ring, is positioned within a region which ranges circumferentially between 10xc2x0 in a direction where the orbiting scroll wrap is extended and 80xc2x0 in a direction where the orbiting scroll wrap is wound up, when measured from a straight line connecting a center of a base circle of the orbiting scroll wrap with an outer end of the orbiting scroll wrap.
According to still another aspect of the present invention, there is provided an asymmetric scroll compressor including an orbiting scroll having an end plate and a boss part which are concentrically formed and possessing a wrap which is formed on an upper surface of the end plate and has an involute curve-shaped configuration, an Oldham ring arranged on a lower surface of the orbiting scroll in such a way as to prevent the orbiting scroll from being rotated, and a fixed scroll covering an upper portion of the orbiting scroll and having a wrap which has an involute curve-shaped configuration and is engaged with the wrap of the orbiting scroll in a manner such that compression chambers are defined between the wraps of the orbiting and fixed scrolls by rotating motion of the orbiting scroll, the wrap of the fixed scroll further extending within the range of 180xc2x0 than the wrap of the orbiting scroll in a direction where an involute curve extends, wherein, when assuming that a volumetric ratio designates a ratio between an intake volume and a volume upon undertaking discharge, a first volumetric ratio of a first compression chamber which is defined between an inner surface of the fixed scroll wrap and an outer surface of the orbiting scroll wrap, is made larger than a second volumetric ratio of a second compression chamber which is defined between an outer surface of the fixed scroll wrap and an inner surface of the orbiting scroll wrap.
According to yet still another aspect of the present invention, the first volumetric ratio of the first compression chamber is made larger than the second volumetric ratio of the second compression chamber by at least 0.1.